Thrust-producing apparatus such as presses and the like



Dec. 18, 1956 P. E. ASHTON 2,774,217

THRUST-PRODUCING APPARATUS SUCH AS PRESSES AND THE LIKE Filed July 51950 3 Sheets-Sheet 2 INVENTOR Pm lzblilfskton.

M ATTORNEY Dec. 18, 1956 Filed July 5. 1950 P. E. ASHTONTHRUST-PRODUCING APPARATUS SUCH AS PRESSES AND THE LIKE 3 Sheets-Sheet 3United States Patent THRUST-PRODUCING APPARATUS SUCH AS PRESSES AND THELIKE Philip E. Ashton, Meriden, Conn. Application July 5, 1950, SerialNo. 172,159 26 Claims. (Cl. 6054.5)

This invention relates to thrust-producing mechanisms, for instancepresses and the like, in which thrust is exerted on a piece of work by aram; and it relates more particularly to presses in which both amechanical linkage and hydraulic thrust-multiplying means are utilizedto provide great mechanical advantage.

An object of the invention is the provision of a thrustproducing devicewhich will attain high working pressures and may be adapted for use inconveniently small machines such as hand-operated presses.

Another object is to provide a thrust-producing device which, during aninitial stage, provides a relatively large movement of the thrust memberunder a comparatively low thrust, and which may be quickly shifted,without reducing the thrust, to succeeding stages for producing amultiplied thrust.

A further object is the provision of sturdy, simple and reliable meansfor controlling the change from one stage of ope-ration to a successivestage. i

A thrust-producing device embodying the principles of the invention hasa plurality of cooperating and interrelated thrust-imparting means, eachoperable to apply thrust to a thrust member which acts upon the work,one of said thrust-imparting means being actuated by reaction from thethrust of another of said thrust-imparting means upon said thrustmember. This may be carried forward into one or more succeedingthrust-multiplying means, although in practice the desired result isordinarily attainable with two such means. The first means ispoweroperable to transmit the power supplied, for instance, by a motoror by hand to the thrust member, which in presses is usually a ram. Suchpower-transmission means or a portion thereof is adapted to move due toreaction of the thrust imparted by it to the thrust member. The secondthrust-imparting means, having a primary element connected to thetransmission means and a multiplied thrust element connected to thethrust member, is actuated by movement of said transmission means toproduce a multiplied thrust on the thrust member. A frame supports,either directly or indirectly, all the operating elements of the device.

An important feature of the invention is the provision of releasablerestraining means operable to hold the powertransmission mechanismagainst substantial movement relative to the frame of the device. This,when functioning, restricts the action of the transmission means toimparting thrust directly to the ram and renders the thrust-multiplyingmeans inoperative. Furthermore, the restraining means may desirably beautomatically operable under a predeterminable load to release thetransmission means for movement which, in turn, brings thethrustmultiplying means into operation so that both means operateconcurrently.

One particularly desirable embodiment of the invention consists of apress having a ram moved only by mechanical linkage until a desiredresistance is met by the ram, whereupon a hydraulic thrust-multiplyingmeans is brought into operation to apply a multiplied thrust to the ram.

An important advantage provided by such a press is that a thrust on theorder of five to ten tons or more can be produced by a convenient,small, compact and relatively inexpensive device. Furthermore, in such apress, the ram can be moved rapidly under no load or under loads withinthe limit of the mechanical linkage. Moreover, when the press is used,for instance, for metal piercing with a punch and die or for openingsome types of molds used in molding plastics, the ram can --bepositively and quickly retracted from the work by operating themechanical linkage in the reverse direction.

The releasable restraining mechanism which, in its most desirable form,in responsive to thrust on the ram, can have a lever control alfordingthe choice of two ram thrust values, at which the change from one stageof operation to another may take place. One of these settings permitsthe change at a low ram thrust value and is useful in metal piercing andsimilar operations where both stages of mechanical advantage are neededas soon as the ram, or a tool mounted therein contacts a work piece. Theother setting brings about the change at a relatively high ram thrustvalue and is of considerable value in cases where a press is used toforce two pieces together, such as pressing a bushing into a hole, whereit is desirable to feel the start of the assembly. This second settingis also of value in using the device in injection molding where a long,rapid stroke at moderate pressure is needed to inject material into themold, and then a short, high-pressure stroke is required to force thematerial into all the details of the mold. For instance, in the firstsetting the change may take place at about lb. ram thrust, cal-ling forvery little effort on the part of the operator and being sufiicient toplace a piercing punch in intimate contact with a piece of metal thatwill require four or five tons of ram thrust to pierce it. The secondsetting would be used where 800 or 1000 lb. of ram thrust is requiredover a distance of one or two inches to fill a mold or to compactmolding powder already placed in a mold, and where thereafter a shortstroke of A to /2 inch is needed at a high ram thrust of four or fivetons to fill all details in a mold or to effect a final compacting of amolding powder, such as phenolic resin.

For other applications, however, the restraining mechanism may be madeto operate manually so that when the desired thrust is attained in thefirst stage, a lever on the restraining means is moved by the operatorto change from simple to compound operation of the press.

Although a thrust-producing device embodying the principles of theinvention is most desirably provided with restraining means which permiteither simple or compound operation, a device without the restrainingmeans is also within the scope of the invention.

The foregoing and other objects of the invention as well as novelfeatures and advantages, will become further apparent from the specificdescription hereinafter.

Apparatus embodying the invention is illustrated in the accompanyingdrawings, in which Fig. 1 is a perspective view, partly in section andpartly broken away, of a small manually operated press embodying theinvention;

Fig. 2 is a plan view of the same with the housing cover removed;

Fig. 3 is a vertical section on the line 33 of Fig. 2;

Fig. 4 is an enlarged detail view of a control valve;

Fig; 5 is a cross-sectional view showing a mechanical latch type ofreleasable restraining means and part of the gear-carrier and taken onthe line 55 of Fig. 3;

Fig. 6 is an elevation of the latch mechanism looking in the samedirection as Fig. 5;

Fig. 7 is an end view of the latch shown in Fig. 6;

Fig. 8 is a detail of parts of the mechanical latch shown in anotherposition of operation;

Fig. 9 is a section of part of a modified cylinder head showing anotherarrangement of the hydraulic valve mechanism;

Fig. 10 is a plan view, having certain parts removed, of anothermodified cylinder head incorporating a hydraulically operated deviceserving the same purpose as the mechanical latch shown in Figs. -8;

Fig. 11 is a cross-section view on the line 11-11 of Fig. and

Fig. 12 is an elevation looking in the direction 12-12 indicated in Fig.10.

In the specific embodiment of the invention shown in the drawings, 16 isthe base on which work may be performed, and upright members 11 and 12,rigidly mounted on base 10, support brackets 13 and 14 securely boltedor welded thereto. This structure forms the frame in which work is doneby the thrust-producing mechanism. Shroud 15, which is secured tobrackets 13 and 14, encloses the lower portion of the thrust mechanism,and strengthens the frame to help prevent bending thereof. Cylinderhousing 16, provided with a cover 17, is securely mounted on bracket 14in such manner as to be capable of transmitting the full reaction fromthrust exerted by the ram to the frame of the press.

Ram 18, protruding through and guided by the bracket 13, may movevertically toward and away from base 10. The lower end of the ram may beadapted in any of several well known ways to carry such tools as arerequired. For instance, one way (not shown) is to bore a hole coaxiallyin the ram to house a tool shank which may be clamped in place by a setscrew threaded into a transverse hole in the ram.

The ram passes through gear-carrier 19, which is slidable thereon andalso on guide rod 20 rigidly supported at its ends by the brackets 13and 14 and having its axis parallel with that of the ram. Gear shaft 21,having gear 22 at one end and star wheel 23 at the otherend, isrotatably supported in gear-carrier boss 24, which protrudes through anelongated opening 25 in shroud 15. The star wheel, gear shaft and gearare rigidly secured together so that torque may be transmitted from thestar wheel to the gear, the gear teeth 26 engaging the teeth 27 of ram18. v

Upon rotation of star wheel 23 in the direction indicated by the arrowshown in Fig. l, the gear-carrier 19 will tend to move upward along ram18 and the carrier guide 20. In order to prevent any substantial amountof movement between the gear-carrier and the frame of the press, so thatthe gear 22 can exert a mechanical thrust on the ram 18 in a mannersimilar to an ordinary mechanical arbor press, gear-carrier 19 isprovided with an extension or tongue 28 projecting from its undersideand adapted to be held by latching means, hereinafter more fullydescribed, mounted on the frame of the press. Tongue 28 passes throughan opening 29 (Figs. 3 and 5) in bracket 13 and is provided at its lowerend with a hard- "ened steel latch plate 30 having beveled latchingfaces 31. A pair of hardened steel latch blocks 32 having faces adaptedto engage the faces 31 of latch plate 30, are carried on pins 33 (Fig.5) and are free to turn thereon. Because the blocks are unbalanced onpins 33, they assume the position shown in Fig. 5 with their undersurfaces resting on pins 34 and 35, Pins 33 are mounted in link sideplates 36 which are in turn supported by pins 37, free to rotate inbearing blocks 38 which are secured to the underside of bracket 13. Pins34 and 35 have reduced-diameter end portions 39 and 40 (Fig. 6),respectively, extending through and free to turn in side plates 36.Holes are cross drilled at the mid-portion of pins 34 and 35 to providesupport for latch bolt 41, which is permitted to slide lengthwise and torotate therein for reasons hereinafter explained. Each blo k 32 has agroove 42 cut across the lower portion to clear parts associated withbolt 41. It now becomes readily apparent that so long as latch blocks 32remain in contact with the faces 31 of latch plate 30, the tongue 28 islocked in the position shown in Figs. 1, 3, 5 or 6, thereby preventingany substantial amount of movement of the gear-carrier 19 relative tothe frame of the press.

The bolt 41 is reduced in diameter at one end for a portion of itslength, thus forming a shoulder 43 (Figs. 5 and 8). The end of thereduced portion is threaded and carries adjusting nut 44 and compressionspring 45 between washers 46 and 47. Washer 47 is adapted to be pressedunder the influence of spring 45 either against pin 35 or against theshoulder 43 of bolt 41 as will be more clearly brought out hereinafter.The pressure exerted on washer 47 by spring 45 is adjustable by means ofnut 44. In order to maintain a desired minimum space between the lowerends of links 36 and between blocks 32, a sleeve 48, mounted on bolt 41between pins 34 and 35, is provided as a spacer for this purpose.

The head 49 of bolt 41, having a handle 59 by which the bolt may berotated, has two pairs of concave faces 51 and 52, each pair beingsuited for mating engagement with the surface of pin 34. When the pairof faces 51 is engaged with pin 34, as shown in Figs. 5-7 inclusive, theshoulder 43 is located just within pin 35 against which washer 47 ispressed by spring 45, and the lower ends of the two links 36 are held asclosely together as spacer 48 will permit. Any movement of the lowerends of the links away from each other will further compress spring 45,which has been pre-compresed by adjustment of nut 44 toward the bolthead. A tension spring 53 (Fig. 6) is attached to the reduced-diameterend portions 39 and 40 of pins 34 and 35 at one end of each and drawsthe links toward each other. Thus, with faces 51 of bolt head 49 inengagement with pin 34, as shown in Figs. 5 and 6, any effort to spreadthe links apart will be resisted by both springs 45 and 53.

If, however, bolt head 49 is turned so that faces 52 are in position forengagement with pin 34, the bolt is per mitted to slide longitudinallywithin pins 34 and 35, and the shoulder 43 will protrude beyond pin 35,as shown in Fig. 8, and is abutted by washer 47 so that the load ofspring 45 is removed from the linkage. In this condition any effort tospread the links apart will only be resisted, within ractical limits, byspring 53. Consequently, an upward pull by tongue 28 against latchblocks 32, which is sufficient to spread links 36 against the tension ofspring 53, will separate latch blocks 32 enough to release tongue 28 sothat gear-carrier 19 is permitted to move relative to the frame of thepress.

If desired, however, when the faces 51 of the bolt head 49 are engagedwith pin 34, nut 44 may be tightened until spring 45 is substantiallysolid, in which case the lower ends of the links 36 are unable to spreadapart enough to open the latch. On the other hand, if bolt head 49 isnow turned so that faces 52 engage pin 34, the latch'will again bepermitted to open under a force greater than the tension of spring 53.

Coming now to the second stage or hydraulic thrustmultiplying portion ofthe press, a pair of cylinders 54 and 55 are located within cylinderhousing 16, the larger of these, 54, being the thrust cylinder and thesmaller, 55, being the boost cylinder. Ram 18 extends into the thrustcylinder 54 and terminates in a piston 56 having a convenient seal, suchas a conventional O-ring. A piston rod 57 has a reduced diameter portion58, fitting in a hole in gear-carrier 19, and is anchored by a cross pin59 against withdrawal. Any downward load on rod 57 is transmitted togear-carrier 19 by the shoulder formed by the reduced diameter portion58. The upper end of rod 57 has an enlarged diameter portion 60, whichforms a piston for the boost cylinder and which also is fitted with aseal, such as an O-ring. The upper ends of the cylinders 54 and 55 areheld in closefitting holes in a supporting member 61 secured to housing16, and their lower ends are located in recesses in bracket 14, which isprovided with openings through which ram 18 and piston rod 57 may pass.

The upper ends of the cylinders are a close fit in annular grooves inthe cylinder head 62, and are sealed therein against leakage by softsynthetic rubber gaskets 63 and 64. The upper ends of the cylinders arechamfered so that the annular space provided permits some flow of thegasket material inward toward the cylinder bores when the head 62 isforced downward by cylinderhead retaining ring 65, which has screwthreaded engagement with the inner wall of housing 16. This constructionis clearly shown in Fig. 3, and in the modified forms of the head shownin Figs. 9 and 11. The above described method of sealing the cylindersin the cylinder head removes any need for precise matching of cylinderheights or the depths of the cylinder head grooves, and will sealpressures in excess of 5000 p. s. i. with very slight screw threadloading of ring 65. The space in prevents leakage of fluid from saidreservoir.

The cylinder head 62, shown in Figs. 1 and 3, has an unobstructedpassage 67 connecting the two cylinder bores so that identical pressureconditions are maintained within the cylinders at all times. Passage 68is drilled from the outside of housing 16 through the cylinder head tocylinder 54 to provide a suitable connection for a pressure gauge. Inthe drawings, no gauge is shown, and passage 68 is closed off by athreaded plug. A port 69 is provided in the under face of the cylinderhead, and holes 70 aredrilled therefrom to the upper side of the head,forming fluid passage between the reservoir and cylinder 54. A valve 71,guided in a drilling in the cylinder head, is arranged to close port 69and is urged by spring 72, acting through washer 73 and cotter pin 74,to its closed position. Spring 72 is so proportioned that valve 71 willbe opened by suction created by the downward movement of either piston56 or piston 60. The difliculties commonly encountered in obtainingsatisfactory valve seating in hydraulic service are overcome by facingthe valve with a semi-rigid material, such as nylon, and shaping thisfacing so that it has a very narrow surface of initial contact with themating surface of the cylinder head. This provides a reliable seal atlow pressures and, although the shaped face of the seat is flattened athigh pressures, it resumes its initial shape when pressure is released.A suitable construction of valve 71 is shown in Fig. 4, where the headof the valve is shaped to afford a groove into which seating ring 75 issnapped. The upper lip of the groove is made only a few thousandths ofan inch smaller in diameter than the inside diameter of port 69, inwhich it is housed when the valve is closed, in order to preventextrusion of the seating ring between the valve and the wall of port 69,under the influence of high pressure.

A valve leakage supporting member 76 (Figs. 2 and 3), mounted on thecylinder head 62, acts as a bearing for rocking shaft 77, having levers78 and 79 rigidly attached thereto. Lever 78 is adapted to depress thestem of valve 71 and thereby open the valve when lever 79 is pulleddownwardly by pull rod 80 which is movable vertically under theinfluence of gear-carrier 19, as will be explained hereinafter. Thestrength of spring 72 is suflicient to close the valve against theotherwise unbalanced weight of the levers. Pull rod 80, having a head 81at its lower end and an adjusting nut 82 at its upper end, extendsdownward from lever 79, on which nut 82 rests, through a gland 83 in thecylinder head, through bracket 14 and through a clearance hole in lug84- (Figs. 1 and 5) of gear-carrier 19; A compression spring 85,restrained between nut 86 and gland nut 87, serves to urge rod 80 upwardand to relieve valve spring 72 of the weight of the rod and the frictioncaused by gland 83.

As is clearly shown in Fig. 5 there is a small gap between latch platefaces 31 and latch blocks 32 when the gear-carrier 19 is at its lowestpoint. This gap permits a limited upward movement of gear-carrier 19prior to restraint of such motion by mutual engagement of the latchingsurfaces. The eflective length of pull rod 80 is adjusted by nut 82 sothat, with gear-carrier 19 at its lowest point, lug 84 engaging rod head81 causes the valve 71 to be held open. When the gear-carrier is movedupward until faces 31 engage their mating faces on blocks 32, the pullrod is also moved upward by spring 85, and this movement is sufficientto permit valve 71 to close.

Having fully described the various parts of one specific embodiment ofthe invention shown in the drawings, its operation will now be discussedin detail. Assuming that there is no work piece under the ram and thathydraulic fluid fills the cylinders above the pistons and the reservoirto the fluid level indicated approximately by the broken line L in Fig.3, and also that gear-carrier .19 is'at its lowest point, rotation ofthe star wheel 23,

in the direction indicated by the arrow in Fig. 1, will cause ram 18 andits piston 56 to descend, and hydraulic fluid will be drawn past valve71 into the cylinders. Reversal of the star wheel will reverse thisaction, and fluid will be returned to the reservoir since valve 71 isheld open by the valve levers. Should there be suflicient frictionbetween the seal of piston 56 and the wall of the thrust cylinder, orbetween ram 18 and its support in bracket 13, rotation of the star wheelin the direction shown will first cause gear 22, together with itscarrier 19, to climb ram 18 until the mating latch parts 30 and 32engage each other and arrest this move ment. In this condition valve 71is free of the influence of pull rod 80, and 71 may close; but, sincethe valve is subject to opening by suction, descent of the ram willagain draw fluid into the cylinders. Reversal of the star wheel willcause the gear-carrier to descend and open the valve by means of pullrod 80, thus permitting fluid to pass upward past the valve as the ramascends.

Operation with a work piece under the ram will bethe same as above untilthe ram meets so much resistance to its descent that the upward reactionthrust of the gearcarn'er causes the beveled faces of the latch members30 and 32 to force links 36 apart against the pressure of spring 53 and,if bolt head 49 is set as shown in Figs. 5-7, also against spring 45.When links 36 are moved far enough apart, blocks 32 become disengagedfrom faces 31 of latch plate 30. Gear-carrier 19 is then free to moveupward along ram 18 and guide-rod 20 under the influence of the reactionof gear 22 on the ram. A reaction thrust will now be transmitted toboost piston 60 which will, in turn, create a pressure on the fluidtrapped in the cylinders by the closing of valve 71, which pressure willexert a downward thrust on ram 18 through the piston 56.

The hydraulic thrust on the ram will bear the same relationship to thereaction thrust on piston 60 as does the area of piston 56 to the areaof 60, and the distance traveled by 56 relative to the travel ofthegear-carrier will be in inverse proportion to the above relationship ofthe piston areas.

It is important to note that, since valve 71 is closed beforegear-carrier 19 is released by the restraining means, there is norelaxation of thrust on the ram during the change from simple tocompound operation, even though the force which has to be applied to thestar wheel 23 to maintain the original thrust on the ram is reduced.This is due to the fact that the fluid trapped in the cylinders 54 and55 cannot escape and thus prevents any upward movement of the ram.

If the star wheel is then turned in the reverse direction thegear-carrier will descend until it reaches its lowest point and opensvalve 71 as hereinabove described. As

and 55 respectively.

7 the gear-carrier approaches its lower position, the latch plate 30will pass downward between latch blocks 32 and will tilt them, asindicated in Fig. 6 by broken lines, until it clears the lower edges ofthe blocks, which will then return to their normal position, beingturned on their pins 33 by the unbalanced weight of their outerportions. Continued rotation of the star wheel in this same directionraises ram 18 and piston 56, since the gear-carrier 19 has returned toits lowest position and rests on bracket 13 of the press frame. Thefluid in cylinder 54 flows back into the reservoir because valve 71 isheld open by rod 80 working through the valve linkage 77, 78 and 79. Ifthe tool attached to the lower end of the ram encounters any resistancein being removed or stripped from the work, as will happen for instance,in metal piercing with a punch and die, reverse rotation of the gearwill exert a positive upward force on the ram thus quickly and easilyextractingthe tool from the work.

From the foregoing description of a hand operated press according to theinvention, it is obvious that the mechanical latch mechanism 28-53,although herein above described as operating automatically when apredetermined thrust is exerted on the ram by gear 22, can be readilyadjusted for manual operation. This is accomplished, as previouslymentioned, by placing bolt head 49 in the position shown in Fig. 5, andtightening nut 44 until spring 45 is substantially solid. The latch isthen locked in its closed position, since spring 45 cannot be furthercompressed to the extent necessary to permit blocks 32 to clear latchplate 30. In order to release the latch, bolt head 49 is rotated 90 toengage faces 52 with pin 34, as shownin Fig. 8-. Since spring 53 isrelatively light, it is easily overcome by any substantial pressure onthe latch and, under these conditions the latch may be considered, forall practical purposes, as open. Manual operation of the latch is thusaccomplished without difliculty whenever desired.

In the device as above described, there is only one valve, and anybackward motion of the star wheel will result in a relaxation of thethrust of the ram whether in hydraulic boost action or only in directmechanical action. This relaxation is not objectionable in many cases,such as when the press is being used for piercing, shearing or bendingmetal, but in the molding of some plastics it is essential that thepress be locked under thrust pressure while the material in the mold iscured. This end may be accomplished by modification of the cylinder headand valve and the addition of other parts as shown in Fig. 9. In thismodified form the cylinder head 62a is seated on cylinders 54 and 55 asbefore described and has a vertical assage 33 leading from the reservoirto boost cylinder 55. The lower portion of this passage iscounter-drilled to provide space therein for a conventional ball checkvalve 89, consisting of a valve ball 90 urged by a spring 91 against aseat 92, all held in place by a retainer cup 93 which is threaded intothe enlarged portion of passage 88 and has an opening 94 in its lowerend. This intake valve will permit hydraulic fluid to flow from thereservoir to the boost cylinder through passage 8 but it will not permitfluid to thereby return to the reservoir. .A horizontal passage 95 isdrilled in the cylinder head and plugged at its outer end. To thispassage are drilled vertical passages 96 and Q7, which connect with thebores of cylinders 54. Passage 96 is counter-drilled and provided with adischarge valve 98, which is identical with valve 89 and which permitsflow of hydraulic fluid therethrough only from the boost" cylinder thethrust cylinder 54.

The valve operating mechanism, including support member 76, rockingshaft 77, levers 78 and '79 and pull rod 86 is arranged exactly asdescribed in connection with Figs. 2 and 3, but these parts are notshown in Fig. 9 for purposes of clarity.

A valve 100, which is generally similar to valve 71 previously describedand which has generally similar functions, is urged to closed positionby'a spring 101, acting through washer 102, and a spring retainer ring103, which is snapped into a circumferential groove 104 in the stem ofvalve 100. The valve may be opened by suction exactly as in the case ofvalve 71. Three coaxial drillings are provided axially through valve100.- The largest diameter drilling forms a valve chamber 105. Theintermediate drilling forms a passage 106 connected by cross drillings107 with the fluid reservoir by Way of port 108 and passages 109 in thecylinder head 62a. The smallest drilling 110 serves to guide a push-rod111 Within the stem of valve 1%. A valve 112 of similar construction tovalves 89 and 98 has a valve ball 113, a valve seat 114 andvalve-closing spring 115 maintained in their places by retainer cup 116,which is threaded into chamber 105 and has an opening 117 in its lowerend. The valve seats, used in valves 9, 98 and 112, are preferably madeof a semi-rigid synthetic material similar to that used for valve seatring of valve 7L hereinbefore described.

The push-rod 111 slides freely within the stem of valve 100 with itslower end resting on valve ball 113 and its upper end protrudingslightly above the valve stem. The valve operating mechanism, comprisingshaft 77, levers 78 and 79, and pull-rod are used with this modifiedconstruction in the same manner as in the previouslydescribedembodiment, except for the fact that lever 78 contacts push-rod111 and opens valve 112 before it opens valve 100. 1

In the operation of this modified form of the invention, the unmodifiedparts of the press function exactly as they did in the first embodimentdisclosed. After the gearcarrier 19 has been released by the opening ofthe latch in the manner hereinabove described, it moves upward 98 intothe thrust cylinder 54. Since valves 89,

and 112 are closed, flow of the fluid from the cylinders 54 and 55 intothe reservoir is prevented, and downward pressure on the ram isdeveloped. If the star wheel 23 is now released the pressure on the ramwill be maintained (assuming that the work under the ram does not permitthe ram to move), since valves 98, 100 and 112 are all closed. In thiscondition the ram is locked. Rotation of the star wheel in the reversedirection causes the boost piston to descend, valve 89 will be opened bysuction and a new charge of hydraulic fluid will be drawn into the boostcylinder. Oscillation of the star wheel will cause the boost piston topump fluid into the thrust cylinder and the ram may be traversedhydraulically for its full stroke by this means, provided that thestar'wheel is not turned back far enough to cause the lug 84 on thegear-carrier to engage the head 81 and to force pull-rod 80 downward.

When pull-rod 80 is forced downward the valve opening lever 78 willdepress push-rod 111, opening valve 112 before opening valve 100. Thisis necessary since valve 100, like valve 71, must be large enough topermit the free flow of fluid back to the reservoir when the ram travelsupward. Valve 100 is then too large to be opened against the hydraulicpressure on a locked ram,

but valve 112 may be made small enough to be opened readily against highpressure and thus to serve as a pressure spill valve. In a press havinga two inch diameter thrust piston and working up to 5000 p. s. i. (7.85tons thrust on the ram), it has been found that a inch diameter issuitable for port 108 and that inch is suitable for the diameter of thepassage through valve seat 114. It is thus possible to spill 5000 p. s.i. pressure from the thrust cylinder with less than 100 lb. load onpush-rod 111, whereas over 1500 lb. load would be required to open valve100 directly against this pressure.

The foregoing description of specific embodiments of the invention hasassumed that the mechanical latch illustrated in detail in'Figs. 5-8 isused to change from simple tocompound operation of the press. Theinvention is obviously not limited to this construction. Inorder toillustrate another practical means which may be substituted for themechanical latch, Figs. 1012 show a hydraulically operated mechanism,serving the function of the mechanical latch hereinabove disclosed and.oifering certain additional advantages such as low initial cost andgreater adaptability to othertypes of framework in which the operativeunit may be mounted. Furthermore, the hydraulically operated restrainingmechanism is not sensitive to gravity as is the mechanical latch and,for this reason, it will operate with an inverted or horizontal unitwithout modification. 7

Figs. 10, 11 and 12 show a cylinder head having all of the functions ofthat shown in Fig. 9, but modified for the incorporation of thehydraulic device which may be substituted for the mechanical latchmechanism shown in Figs. to 8. In a construction employing the hydraulicrestraining means, none of the latch parts previously described andhaving reference numerals 30m 53 inelusive are required; nor aregear-carrier extension 28 and hole 29 in bracket 13 needed. The cylinderhead 62b is seated on cylinders 54 and 55 and is retained in housing 16by ring 65 having gasket 66. This construction also has valves 89, 98,100 and 112 together with valve control linkage including shaft 77,lever 78, pullrod 80 and push-rod 111 as previously described, but lever120 is substituted for lever 79 as its shape difrers slightly from thatof the latter inorder to accomplish an additional function hereinafterdescribed. The position of valve 180 is indicated in Fig. 10 but hasbeen omitted from Figs. 11 and 12 to clarify them. A vertical passage121 (Fig. 11) leads from the boost cylinder 55 to passage 122 in valvehousing 123 having a cylinder 124 into which passage 122 discharges. Thebottom of cylinder 124 has a coaxial opening125 communicating, throughpassage 126 in cylinder head 62b, with valve' 98 having functionshereinbefore described. The junction of cylinder 124 and opening 125forms a seat for the valve portion 127 of piston 128 which is slidablysupported in the cylinder and has a convenient seal such as an O-ringindicated by 129. A plug 130 serves to seal the open end of passage 122,and resilient gaskets 131 and 132, housed in suitable cavities, seal thejunctions. of passages 121 with 122 and 125 with 126 while permittinghousing 123 to .be rigidly held in metal to metal contact with cylinderhead 62b by means of screws 134 (Figs. 10 and 12). Y

A stud135 is secured to the cylinder head andpasses through a suitableopening in one end of a lever 136. An adjusting nut 137 is threaded .onthe stud at its upper end, which protrudes through an opening providedin the cover of the reservoir. A cam block 138 having a handle 139 isrotatably mounted on stud 135 but is not threaded thereon. Notches 140,141, 142, of varying depth are provided in the under face of camblock138 and are adapted for individual engagement by a mating projection 143on the top face of a second cam block 144. Cam block 144 is slidablymounted on stud 135 for vertical motion only and is restrained fromturning thereon by key 145, which slides in a keyway in stud 135. Awasher 146 is placed between nut 137 and cam block 138 to facilitateindependent rotation of these members. A compression spring 147 islocated on stud 135 between cam block 144 and the lever 136 which issupported by pin 148 in bearing posts 149 mounted on or integral withhousing 123. In Fig. 10,-the cylinder housing cover 17 and springadjusting members 137 to 145 have been removed in order to show theparts below more clearly in this view. Movement of nut 137 along thestud or varying the position of the projection 143 on cam block 144 innotches 140, 141 and 142 of cam block 138 will decrease or increase thepressure of spring 147 on lever 136 which bears on piston 128, in themanner clearly '10 shownin Fig. l1 and thus presses valve portion 127 onits seat.

The end of lever 136 remote from stud 135 is shaped to provide a latchportion 150 adapted for engagement by catch 151: (best seen in Fig. 12),which is pivoted on pin 152 mounted on housing 123. Catch 151 is urgedcounter-clockwise, as indicated by an arrow in Fig. 12, by torsionspring 153 having one end engaging pin 154 secured to housing 123, .andthe other end bearing on catch 151. Lever 120, which is secured to shaft77, engages an arm 155 of catch 151 so that depression of 120 will causethe catch to turn against the influence of spring 153 and in a clockwisedirection as viewed in Fig. 12, while elevation of 120 will permit thecatch to be turned in the opposite direction by the spring 153. If thelatch portion 150 of lever 136 is pressed toward the cylinder head, itmay be engaged and held by catch 151 until lever 120 is depressed inorder that catch 151 will free latch portion 150, thus releasing lever136 Operation of a press incorporating the device just described isgenerally similar to the operation of the press as previously set forthexcept that the upward motion of the gear-carrier will be restrained byfluid trapped in cylinder 55 and passages 121 and 122 between piston 60,valve 127 and piston 12%. Thus, pressure developed on the fluid byreaction thrust, transmitted by gear-carrier 19 to piston 60 will tendto force piston 128 upwards and to open valve 127, thereby permittingthe flow of fluid into thrust cylinder 54 via valve 98. Assuming thatgearcarrier 19 is at its lowest point, rotation of star wheel 23 in theproper direction will cause ram 18 to descend and fluid will be drawnfrom the reservoir, past valve 100 and into thrust cylinder 54, valve100 being held open by pull-rod through lever 120, rocking shaft 77 andlever 78 as previously described. Any resistance to movement of the ram'18 will develop reaction on the gear-carrier, and this reaction will beopposed by fluid trapped in boost cylinder 55. When the reaction becomessufliciently great, fluid pressure will cause piston 128 to move againstthe pressure of spring 147 acting through lever 136, and valve 127 willbe lifted from its seat permitting some of the fluid under pressure topass into the cylinder 54. This flow of fluid will permit carrier 19 torise and release the tension on pull-rod 80, thus allowing valve toclose.

Hydraulic pressure will then be imparted to the ram by pressuredeveloped in cylinder 54. Should sufficient hydraulic pressure bemaintained, piston 128 will continue to move against the pressure ofspring 147 and the latch portion 150 of lever 136 will move toward thecylinder head 62b until it is engaged by catch 151, which at this pointis not held by lever 120, due to the fact that pull rod 80 is releasedby gear carrier 19. Further movement of latch portion 150 is preventedby its contact with the lower face of the notch in catch 151 and lever136 will be held stationary, thus releasing piston 128 and valve portion127 from the influence of spring 147 so that the valve portion 127 canoffer no further resistance to flow of fluid from cylinder 55 tocylinder 54 even though piston 60 is reciprocated to draw more fluidfrom the reservoir through valve 89 in order to pump it to cylinder 54.If gear-carrier 19 is returned to its lowest point, it will causepull-rod 80 to descend and depress lever 120. As a result, valve 100will be opened, and at the same time lever will strike arm 155, turningcatch 151 on its pivot releasing lever 136 and allowing spring 147 tocause valve 127 to close.

It should 'be noted that the eflective area of piston 128, on whichfluid pressure may act prior to the opening of valve 127 is less thanthe efiective area when the valve is off its sea-t. Therefore, theseareas may be so proportioned that spring 147 can be relatively light yetstill be adequate to hold the hydraulic restraining mechanism closedagainst heavy reaction loads but, once the valve 127 is opened and valve100 is closed, only aslight reaction load will be needed to causefurther movement of piston 128 suflicient 11 to allow catch 151 toengage latch portion 150 and thus to obviate the necessity for a heavyreaction load when not needed.

The modification illustrated in Figs. l12 is capable of rapid adjustmentfor automatic operation at high or low reaction loads and for manualoperation similar to that of the mechanical latch previously described.It the cam blocks 13S and 144 are engaged so that the projection 143 isin the deepest notch 140 as shown in Fig. 11, the spring 147 will beunder only a low compression load, and valve 127 will open when the ram18 first meets any appreciable resistance from the work. By turning camblock 138 by means of handle 139 so that the projection 143 mates withnotch 141, a higher load is placed on spring 147, thereby requiring ahigher reaction load from ram 18 to lift valve 127. Further rotation ofhandle 139 brings notch 142 into engagement with projection 143. In thisposition spring 147 is substantially solid and the press can not operatehydraulically until the cam blocks are returned to either of the firsttwo positions of engagement.

Further adjustment of the load on spring 147 can be obtained by turningdown or unscrewing adjusting nut 137 on the upper end of stud 135. Thus,an infinite number of settings for releasing the hydraulic restrainingmeans may be obtained by first placing the cam block 138 at theapproximate setting desired and then making finer adjustments by meansof nut 137.

While the invention has been disclosed as it would be used in a smallmanually operated press, it is obvious that it may be readily adapted toother applications, such as work holding clamps or Vises. By simplemodifications of the hydraulic fluid reservoir and the mechanical latch,where this is used, the device may be disposed horizontally or it may beinverted so that the ram can carry a rising platen.

What is claimed is:

l. A thrust producing device comprising, in combination, a supportingframe, a thrust member mounted thereon for movement relative thereto,power-transmission means carried by said frame and movable relativethereto, said power-transmission means having a member in engagementwith said thrust member for imparting an initial force thereto,thrust-multiplying means carried by said frame having a portionconnected to, and operable by movement of, said power-transmission meansto impart a multiplied thrust to said thrust member, saidpowertransmission means being moved by reaction of the said initialforce imparted by said member to said thrust member whereby saidthrust-multiplying means imparts a multiplied thrust to said thrustmember.

2. The device set forth in claim 1, wherein said thrustmultiplying meanscomprises a primary element operatively connected to saidpower-transmission means and a multiplied thrust element connected tosaid thrust member, movement of said power-transmission means impartingsuch reaction to said primary element.

3. The device set forth in claim 2, which further includes releasablerestraining means operable to hold said power-transmission means againstsubstantial movement relative to said frame and restricting its actionto imparting said initial force to said thrust member, saidthrust-multiplying means being inoperative while said power-transmissionmeans is restrained but being operable upon release of said transmissionmeans from said restraining means.

4. The device set forth in claim 3, which includes a part carried bysaid power-transmission means and wherein said releasable restrainingmeans comprises a mechanical latch secured to said frame and operable torestrainingly engage said part. 7 e

5. The device set forth in claim 4, wherein the latched parts aredisengageable when said reaction has reached a predetermined magnitude.

6. The device set forth in claim 1,, which further in cludes releasablerestraining means comprising a hydraulic mechanism operable to hold saidpower-transmission means against substantial movement relative to saidframe and restricting its action to impartingsaid initial force to saidthrust member, said thrust-multiplying means being inoperative whilesaid power-transmission means is so restrained.

7. A thrust producing device comprising a frame and a thrust membermovably supported thereby and adapted to engage the work, first andsecond thrust-imparting means supported by said frame, each of saidmeans 'having provision to impart thrust to said member, said firstthrust-imparting means engaging said member for imparting thrust theretoand having a part movable relative to said frame by reaction from saidthrust, said second thrustimparting means having an operating portionconnected to and movable by said part for imparting an added thrust tosaid member when said part is moved by said reaction.

8. A device as set forth in claim 7 having a releasable restrainingmeans supported by said frame and engaging said movable part to restrainit from substantial movement and thereby preventing the operation ofsaid second thrustimparting means.

9. In a thrust-producing device, a frame, a ram supported by said framefor longitudinal movement relative thereto, thrust-imparting meanssupported by said frame and comprising a mechanical linkage engagingsaid ram for applying initial thrust thereto, said thrust-impartingmeans having a portion movable with respect to said frame under reactionfrom the initial thrust applied by said thrust-imparting means to saidram, and hydraulic thrust-imparting means supported by said frame andcomprising fluid-displaci-ng means and fluid-pressure-actuated means,said fluid-displacing means being actuated by movement of said movableportion in response to the reaction of said initial thrust, and saidfluid-pressure-actuated means being adapted to apply increased thrust tosaid ram when fluid under pressure is supplied thereto by saidfluid-displacing means.

10. A thrust-producing device comprising, in combination, a supportingframe, a ram mounted thereon for rectilinear thrust movement relativethereto, power-transmission means ca-rried by said frame and movablerelative thereto in a rectilinear path parallel to said thrust movement,said transmission means having direct mechanical thrust-impartingengagement with said ram, releasable restraining means operable to holdsaid transmission means against substantial movement relative to saidframe and restricting its action to imparting thrust to said ram,thrust-multiplying means carried by said frame, having a primary thrustelement connected to said transmission means and a multiplied-thrustelement connected to said ram, said thrust-multiplying means beinginoperative while said transmission means is held by said restrainingmeans, but being actuated upon release of said transmission means bymovement thereof due to reaction of the thrust imparted by it to saidram.

11. The device set forth in claim 10, wherein a gear rack is providedrigid with said ram, and said transmission means comprises a gearcarrier and a driven gear carried thereby in operative engagement withsaid. gear rack.

12. The device set forth in claim 11, wherein said thrust-multiplyingmeans is a hydraulic system.

13. The device set forth in claim 12, wherein the hydraulicthrust-multiplying means comprises relatively small and large cylinderswhich are intercommunicating, a piston-connected to said gear-carrierand operable in said small cylinder to displace hydraulic fluid to saidlarge cylinder, and a second piston connected to said ram and operablein saidlarge cylinder to impart thrust to said ram.

14. The device set forth in claim 13, which further includes a hydraulicfluid reservoir communicating with saidcylinders to supply fluidthereto, valve means controlling such communication between saidreservoir and said cylinders operable to isolate either or both saidcylinders from said reservoir, said valve means being urged to closedposition by fluid pressure in said cylinders, resilient means furtherurging said valve means to closed position, and valve-actuating meansoperable by movement of said transmission means to open at least a partof said valve means.

15. The device set forth in claim 14, wherein said releasablerestraining means comprises a mechanical latch secured to said frame andsaid gear-carrier has a part movable therewith, said mechanical latchbeing operable to restrainingly engage said part.

16. The device set forth in claim 15, wherein said mechanical latch isoperable to release said part when said reaction has reached apredetermined value.

17. The device set forth in claim 10, wherein said thrust-multiplyingmeans is a hydraulic system comprising relatively small and largecylinders which are intercommunicating, a piston connected to saidtransmission means and operable in said small cylinder to displacehydraulic fluid to said large cylinder, and a second piston connected tosaid ram and operable in said large cylinder to impart thrust to saidram; and said releasable restraining means comprises valve meansdisposed in the intercommunication between said small and largecylinders and operable to isolate said cylinders one from the other, andresilient means capable of urging said valve means to isolating positionwhereby said movement of said transmission means is restrained by thefluid trapped in said small cylinder.

18. A device as set forth in claim 9, wherein saidfluid-pressure-actuated means comprises a cylinder having a pistonconnected to said ram, and wherein said hydraulic thrust-imparting meansfurther includes a fluid reservoir communicating with said cylinder, avalve between said reservoir and said cylinder being urged to closedposition by fluid pressure in said cylinder, and valve actuating meansoperable by said movable portion of said first mentionedthrust-imparting means to open said valve to permit flow of fluid fromsaid cylinder to said reservoir.

19. A thrust producing device comprising, in combination, a supportingframe, a ram mounted thereon for rectilinear movement relative thereto,power-transmission means carried by said frame and having a portionrotatable relative thereto, said transmission means having thrustimparting engagement with said ram, thrust-multiplying means carried bysaid frame and comprising a hydraulic cylinder With a piston operabletherein and connected to said ram to impart thrust thereto, pumpingmeans connected to said transmission means for pumping hydraulic fluidunder pressure to said cylinder, and a fluid reservoir communicatingwith said cylinder and said pumping means, said pumping means having anintake passage connected to said reservoir and a fluid discharge 1passage connected to said cylinder, said pumping means being operable tosupply fluid under pressure to said thrust-multiplying means by movementof said rotatable portion of said power-transmission means due to the 14thrust imparted by said power transmission means to said ram.

20. The device set forth in claim 19, which further includes apressure-operated valve between said pumping means and said cylinder forpreventing the flow of fluid therebetween until a predetermined pressureis built up by said pumping means.

211. The device set forth in claim 20, wherein said pressure-operatedvalve is provided with latch means for maintaining it in open position.

22. The device set forth in claim 21, which further includes a valvebetween said reservoir and said cylinder, and valve-actuating meansoperable by said transmission means to open said last-mentioned valvewhile at substantially the same time releasing said pressure-operatedvalve from said latch means.

23. A thrust-pr0ducing device comprising, in combination, a supportingframe, a ram mounted thereon for rectilinear thrust movement relativethereto, power-transmission means carried by said frame and movablerelative thereto, said transmission means having thrust impartingengagement with said ram, thrust-multiplying means carried 'by saidframe and comprising relatively small and large cylinders which areintercommunicating, a piston connected to said transmission means andoperable in said small cylinder to displace hydraulic fluid to saidlarge cylinder, a second piston connected to said ram and operable insaid large cylinder to impart thrust to said ram and a fluid reservoircommunicating with said cylinders, -a valve between said reservoir andsaid small cylinder adapted to permit flow of fluid only from saidreservoir to said small cylinder and a second valve between saidcylinders adapted to permit flow of fluid only from said small cylinderto said large cylinder, said thrust-multiplying means being actuated bymovement of said transmission means due to reaction of the thrustimparted by it to said ram.

24. The device set forth in claim 23, which further includes apressure-operated valve between said cylinders for preventing the flowof fluid from said small cylinder to said large cylinder until apredetermined pressure is built up in said small cylinder.

25. The device set forth in claim 24, wherein said pressure-operatedvalve is provided with latch means for maintaining it in open position.

26. The device set forth in claim 25, which further includes a valvebetween said reservoir and said large cylinder, and valve-actuatingmeans operable by said transmission means to open said last-mentionedvalve while at substantially the same time releasing said pressureoperated valve from said latch means.

References Cited in the file of this patent UNITED STATES PATENTS775,853- Philipp et al. Nov. 22, 1904 1,659,157 Prouty Feb. 14, 19281,727,626 Adkisson Sept. 10, 1929 2,451,730 Greenlee Oct. 19, 1948

